How to toggle Clipboard "Sync across devices" switch OFF with gpo/intune/registry

[Mari-2019]

I'm trying to figure out how to toggle "Sync across devices" option Off in Settings > System > Clipboard. Been using Windows 10 1903 and 1909. 

Settings like: 

Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\System

AllowCrossDeviceClipboard = 0, don't work since it only greyed the option but doesn't switch the toggle to Off.

Also tried 

HKEY_CURRENT_USER\Software\Microsoft\Clipboard

CloudClipboardAutomaticUpload = 0, which doesn't have any impact.

Thanks in advance!

[#2]

Hi,
you mentioned "don't work since it only greyed the option but doesn't switch the toggle to Off."

what if you manually turn off clipboard syncing again and then use that registry key to grey it out and keep it turned off?

by default it is off so if you just use that registry key, it will stay off and users won't be able to turn them on again.